A search entry often carries no `format`, so `format_of(None)` produced
`Other("")`, that was stashed at search time and handed back as the
download's format, and conversion had no parser to pick:
4073669 could not be converted from to SRT: no parser for ""
`POST /download` takes `sub_format`, and the API converts on its side, so
asking for srt makes the answer srt whatever the uploader posted. The
format guessed from the search entry is dead weight and goes with it.
The download mock matched only `file_id`, so it never exercised what the
real API returns.
Closes#272
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Miguel Palhas
d97cdfd557